Socket 1->Socket 2, 3 or 6 Adapter?

[Raven]

My Presario 425 has a Socket 1 for the "upgrade processor" which currently holds an Am486-100. I've got two chips on the way to try in it, an Evergreen Am5x86-133 (has voltage converter built in so will work on Socket 1) and a Cyrix 5x86-100. I also just received a Pentium Overdrive, but while it was on its way I realized they require Socket 3 and my machine does not have this.

At first I figured I'd just stick it in another machine, but then I was wondering if there was an adapter, or if an adapter could be made, to allow a Pentium Overdrive (Socket 2 minimum, also Sockets 3 and 6) to operate in a Socket 1 board. Anybody?

If not then no big deal, I'll put it in another machine and know that the max I can get out of this machine will likely be a Cyrix 5x86-133 (if I can get a hold of one).

 

[Agent Orange]

Raven - Your thoughts on this about the Pentium Overdrive:
I bought a new (unused) Computrend Premio 486 mobo today. Its still in the box with the manual and a few bags of cables and stuff. The guy was asking $75 on the net and he took my offer of $40. It'll do any cpu up to a AMD 5x486, which I believe is rated at @ 160 Mhz. The board is mix of VL and PCI slots with a max of 64 MB of 72-pin RAM. I spent a couple of hours today digging into the 'why-for's' of going with a P24 Overdrive. What I deduced was the Overdrive chips were mainly for older 486 mobo's locked in at 25 or 33 Mhz. In other words, just an upgrade path for a those lesser boards. According to a couple of old forums, everyone said that they run slower than say a 80486 DX4/100. Although, they're supposed to have a larger built in L1 cache. What's your thoughts on that? I'm kind of thinking that I'll just rip the 80486 DX4/100 out of my Gigabyte GA-486SL and maybe put an Overdrive in that one.

Good luck with your project.

 

[Raven]

I have massively researched the 486 lineup, and generally speaking the fastest 486 chip would either be the Cyrix 5x86 @ 133mhz or the Am5x86 @ 150mhz (super rare) or a 133ADZ OC'd to 160mhz. The Cyrix has the best floating point performance of the 486 chips second only to the Pentium Overdrive, which pales in comparison to other chips that have high clock speeds, but blows past them all in FPU performance. This is why I am interested in that chip. I was curious to see just how smoothly games like Duke3D and Quake could be made to run on a 486-class machine.

After lots of research into why post-Pentium machines "feel" different to me, I deduced that it's because the instructions are translated into micro-ops. The Pentium is essentially an extension of the 486 architecture, with multiple pipelines for instructions and a superior FPU, but the same overall architecture and no translations. When you use an 83mhz POD it should be somewhere in the neighborhood of a DX2-80 or DX4-100 (interestingly DX4 chips are actually 3x multiplier, not 4x...) with an incomparable FPU.

I have an Evergreen 586 (Am5x86-133 SMC w/ voltage regulator so it can go on Socket 1) and a Cyrix 5x86-100 on their way to me, and I intend to benchmark these and the POD against each other to determine which really gives you the best performance. By the time the POD and late Cyrix chips were coming out everyone had moved on to the Pentium architecture, so there isn't much technical documentation comparing these late 486-class options. I'll also benchmark some lower class chips just to get a good baseline and confirm older benchmarks - I'll compare SX vs DX, 25 vs 33mhz, DX vs DX2 vs DX4, and I'll see how much worse an Intel Overdrive 25x4=100mhz fares against the likes of a 33x3=100mhz chip. Just gotta get my hands on all the chips necessary for comparison.

If you have any more questions or would like more detail feel free to ask, I love rambling about 486 systems..

Edit: I just re-read a bit of your post and would like to point out that there's either an Am486 or Am5x86, AMD 5x486 isn't proper notation, but I'd think ya mean 5x86. They are rated at 133 and 150mhz (the 150mhz parts are SUPER rare) and the 133 parts have, in the past, been regularly OC'd to 160mhz without much trouble. I've heard of people OCing ADW chips (the chip notation is AMD-X5-133ADW or AMD-X5-133ADZ) to 160, but the ADZ chips are actually rated for super-high temperatures of up to 85degC where the ADW chips are much lower rated (I don't recall the temp) and should be more prone to failure at higher clocks without ramping the cooling up substantially.

 

[Raven]

I did preliminary benchmarks on the POD chip today, and the early results indicate an over 2x boost in FPU performance with a slightly higher integer performance over a 100mhz DX4 chip.

What I deduced was the Overdrive chips were mainly for older 486 mobo's locked in at 25 or 33 Mhz. In other words, just an upgrade path for a those lesser boards.

Also, that's the Intel OverDrive chips, which are 4x25mhz or 3x33mhz chips by Intel that were marketed for those locked mobos - most mobos at that time were 25 or 33mhz though (these two speeds ended up as the standard for the whole 486 era), the real difference is the socket and voltage support. There are several 486 FSB speeds - 16mhz (unofficial underclock), 20mhz (old and rare, takes 486DX2-40mhz as upgrade), 25mhz, 33mhz, 40mhz (rare, 486DX2-80mhz chips for upgrade), 50mhz (very rare for a stock speed, old DX-50 and DX2-100s go in these). The OverDrives came out early on, before the Pentium even came out afaik, and were intended to get old Socket 1 and "486 Socket" (no official designation) boards up to 100mhz. The Socket 2 was designed with the POD in mind, in the early Pentium days, and the Socket 3 was also compatible. Socket 486 1 and 2 all are 5v, while Socket 3 supports 5v or 3.3v. Most upgrade chips run on 3.3v, including the POD, but the POD has regulation circuitry and so do several other chips (primarily repackaged Am5x86 upgrade kit chips). The Pentium Overdrive requires a newer board, Socket 2 or 3, whereas the other OverDrives do not.

In summary, the early Overdrives were basically really early 3x and 4x multiplier chips for systems that couldn't handle the newer low-voltage upgrade CPUs. The Pentium OverDrive was a later chip that was intended to drag a 486 board up to low-end Pentium performance. Pretty much any Pentium system (except maybe a 60, 66, or 75mhz) will smoke the Pentium OverDrive, but most 486 chips won't (my benchmarks will reveal if any will, for that matter).

If you need any further clarification, feel free to ask.

 

[vwestlife]

AMD 5x486 isn't proper notation, but I'd think ya mean 5x86. They are rated at 133 and 150mhz (the 150mhz parts are SUPER rare) and the 133 parts have, in the past, been regularly OC'd to 160mhz without much trouble.

Either this is a PhotoShop, or maybe AMD actually did make a few 160 MHz 5x86 chips...

Also, the early (pre-"Windows 95") Am5x86 chips were co-branded as "486DX5", so I think that's what A.O. meant to say when he wrote "5x486".

There are several 486 FSB speeds - 16mhz (unofficial underclock)

There actually were some 486SX-16 systems -- most likely created by Intel at the request of manufacturers who wanted a cheaper 486 to sell, and probably just a rebadged 20 or 25 MHz part.

 

[Raven]

I stand corrected on the 16mhz chip, then.

I've never seen a 160-rated part - if it's real then it's likely a 133ADZ rebadged to it's proper max speed at a higher FSB - that's what lots of people did with the 133ADZ chips anyway (and some ADW).

 

[vwestlife]

I've never seen a 160-rated part - if it's real then it's likely a 133ADZ rebadged to it's proper max speed at a higher FSB - that's what lots of people did with the 133ADZ chips anyway (and some ADW).

BTW, I am pretty sure the 5x86-160 shown above is a PhotoShop mockup, because the real 160 MHz part would've been rated as "P90", not "P100". (The 150 MHz 5x86 was rated as "P75+", indicating that it was faster than a Pentium-75 but not as fast as a P90.)

 

[Raven]

Anybody know about my original question?

I'd love to find a way to coerce my Presario 425 into having the Pentium Overdrive chip..

Edit: Here's a good concise pic of the pinouts..

Socket 2 (Supports POD - oldest socket that does):

Socket 1 (What I have):

Glancing around Socket 2 one can see that many pins are reserved, nc, or key pins, so that reduces the workload a bit by sheer pin number if we need to design one of these adapters (if possible).